An ex-con who once tried to kill an NYPD officer in Queens in 2008 was arrested this week for randomly attacking another NYPD officer — only to be freed without bail, authorities and police sources said Monday. 

Isus Thompson, 38, was released after Bronx prosecutors failed to seek bail in the case — prompting an angry response from NYPD Commissioner Dermot Shea in a tweet Monday. 

“Do we have to wait for [Thompson] to kill someone before this is taken seriously?” the disgusted Shea said.

On Sunday, Thompson reportedly struck Officer Kyo Sun Lee, 30, in the head with a black backpack holding a DVD player, adult videos and a small metal safe, according to a criminal complaint and police sources. The officer’s partner also found Thompson in possession of a black metal box-cutter, sources told the New York Post.

Thompson faces three separate assault charges, including at least one felony, giving the judge the discretion to set bail. The suspect also was charged with weapon possession, harassment and resisting arrest, his complaint shows. 

Thompson had previously served two years of a five-year prison sentence after pleading guilty to second-degree attempted murder for stabbing an NYPD officer in Forest Hills in 2008.